Acid-Base and Electrolyte Balance Practice Questions

Q: Metabolic alkalosis is seen in all of the following conditions except:

Uretero-sigmoidostomy. **Explanation:** The correct answer is **Uretero-sigmoidostomy**, as it typically results in **Hyperchloremic Metabolic Acidosis**, not alkalosis. **1. Why Uretero-sigmoidostomy causes Acidosis:** In this surgical procedure, the ureters are diverted into the sigmoid colon. The colonic mucosa is exposed to urine, leading to the active reabsorption of chloride (Cl⁻) in exchange for bicarbonate (HCO₃⁻) secretion into the bowel. This loss of bicarbonate results in a **Normal Anion Gap Metabolic Acidosis (NAGMA)**. **2. Analysis of Incorrect Options (Causes of Metabolic Alkalosis):** * **Prolonged Vomiting:** Leads to the loss of gastric HCl (hydrogen and chloride ions). The loss of H⁺ directly causes alkalosis, while the loss of Cl⁻ leads to "Chloride-responsive" metabolic alkalosis. * **Thiazide Diuretic Therapy:** These drugs inhibit the Na⁺/Cl⁻ symporter in the distal tubule. Increased delivery of Na⁺ to the collecting ducts enhances K⁺ and H⁺ excretion (via aldosterone stimulation), leading to **Hypokalemic Metabolic Alkalosis**. * **Cushing’s Disease:** Excess cortisol has mineralocorticoid activity, leading to increased H⁺ secretion in the distal nephron and potassium depletion, both of which drive metabolic alkalosis. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for NAGMA:** "USED CARP" (Uretero-sigmoidostomy, Small bowel fistula, Extra-chloride, Diarrhea, Carbonic anhydrase inhibitors, Renal tubular acidosis, Pancreatic fistula). * **Saline Responsiveness:** Metabolic alkalosis due to vomiting or diuretics is usually **chloride-responsive** (Urinary Cl⁻ 20 mmol/L). * **Potassium Link:** Alkalosis is almost always associated with **hypokalemia** as H⁺ shifts out of cells in exchange for K⁺ shifting in.

Q: What is the normal route of calcium excretion?

Kidney and Intestine. **Explanation:** Calcium homeostasis is a tightly regulated process involving three main organs: the bone, the kidney, and the intestine. The excretion of calcium occurs primarily through two routes: the **kidneys (renal)** and the **intestine (fecal)**. 1. **Intestinal Excretion (Major Route):** A significant portion of ingested calcium is not absorbed in the small intestine and is excreted in the feces. Additionally, calcium is secreted into the gut lumen via bile and pancreatic juices (endogenous fecal calcium). 2. **Renal Excretion:** Approximately 98-99% of filtered calcium is reabsorbed by the renal tubules. The remaining 1-2% is excreted in the urine. This process is finely tuned by Parathyroid Hormone (PTH), which increases reabsorption, and Calcitonin, which promotes excretion. **Analysis of Options:** * **Option A:** Incorrect because it ignores the significant fecal contribution to calcium loss. * **Option B:** The liver produces bile which contains calcium, but the liver itself is not an excretory organ for calcium; the intestine is the final route. * **Option D:** While pancreatic secretions contain small amounts of calcium, the pancreas is not considered a primary "route" of excretion in the same physiological capacity as the kidney and intestine. **NEET-PG High-Yield Pearls:** * **Net Calcium Balance:** In a healthy adult, fecal excretion (~800 mg/day) is much higher than urinary excretion (~200 mg/day). * **Vitamin D (Calcitriol):** Increases calcium absorption in the intestine and reabsorption in the kidneys. * **Thiazide Diuretics:** Increase renal calcium reabsorption (used in hypercalciuria to prevent stones). * **Loop Diuretics (Furosemide):** Decrease renal calcium reabsorption ("Loop loses calcium").

Q: Low calcium and high phosphate is seen in which condition?

Hypoparathyroidism. ### Explanation The correct answer is **Hypoparathyroidism**. **1. Why Hypoparathyroidism is correct:** The Parathyroid Hormone (PTH) is the primary regulator of calcium and phosphate homeostasis. In hypoparathyroidism, there is a deficiency of PTH, leading to: * **Hypocalcemia:** PTH normally increases bone resorption and renal calcium reabsorption. Its absence leads to low serum calcium. * **Hyperphosphatemia:** PTH is a potent **phosphaturic hormone** (it inhibits phosphate reabsorption in the proximal convoluted tubule). Without PTH, the kidneys retain phosphate, leading to high serum levels. **2. Why the other options are incorrect:** * **Hyperparathyroidism:** This is the exact opposite. Excess PTH causes **Hypercalcemia** (increased bone resorption) and **Hypophosphatemia** (increased urinary phosphate excretion). * **Hyperthyroidism:** While severe thyrotoxicosis can cause mild hypercalcemia due to increased bone turnover, it does not typically present with the classic low calcium/high phosphate pattern. * **Hypothyroidism:** Thyroid hormones have minimal direct impact on acute calcium and phosphate balance compared to PTH. **3. NEET-PG High-Yield Pearls:** * **Pseudohypoparathyroidism:** Presents with the same biochemical profile (Low Ca²⁺, High PO₄³⁻) but with **elevated PTH** levels due to end-organ resistance. * **Chronic Kidney Disease (CKD):** Also shows Low Ca²⁺ and High PO₄³⁻, but is distinguished by elevated PTH (Secondary Hyperparathyroidism) and history of renal failure. * **Vitamin D Deficiency:** Characterized by **Low Ca²⁺ and Low PO₄³⁻** (because PTH rises secondary to low calcium and flushes out phosphate). * **Mnemonic for PTH:** "PTH Puts Phosphate in the Urine" (Phosphaturic action). If PTH is low, phosphate stays in the blood.

Q: Which of the following conditions is typically associated with a normal anion gap?

Renal tubular acidosis. **Explanation:** Metabolic acidosis is categorized based on the **Anion Gap (AG)**, calculated as: $Na^+ - (Cl^- + HCO_3^-)$. The normal range is 8–12 mEq/L. **1. Why Renal Tubular Acidosis (RTA) is correct:** RTA is a classic cause of **Normal Anion Gap Metabolic Acidosis (NAGMA)**, also known as hyperchloremic metabolic acidosis. In RTA, there is either a failure to excrete $H^+$ (Type 1) or a failure to reabsorb $HCO_3^-$ (Type 2). To maintain electroneutrality as bicarbonate is lost, the kidneys retain **Chloride ($Cl^-$)**. Since the increase in chloride offsets the decrease in bicarbonate, the calculated anion gap remains within the normal range. **2. Why other options are incorrect:** * **Diabetic Ketoacidosis (DKA):** Characterized by the accumulation of unmeasured anions (acetoacetate and beta-hydroxybutyrate), which increases the AG. * **Lactic Acidosis:** Occurs due to tissue hypoxia or sepsis; the accumulation of lactate (an unmeasured anion) leads to a High Anion Gap Metabolic Acidosis (HAGMA). * **Starvation Ketoacidosis:** Similar to DKA, the production of ketone bodies increases the concentration of unmeasured anions, resulting in HAGMA. **Clinical Pearls for NEET-PG:** * **Mnemonic for HAGMA:** **MUDPILES** (Methanol, Uremia, DKA, Propylene glycol, Iron/INH, Lactic acidosis, Ethylene glycol, Salicylates). * **Mnemonic for NAGMA:** **USED CARP** (Ureterosigmoidostomy, Saline infusion, Endocrine (Addison’s), **Diarrhea**, **RTA**, Pancreatic fistula). * **Key Distinction:** Diarrhea is the most common cause of NAGMA globally, while RTA is the classic renal cause.

Q: Which of the following is a nonessential amino acid?

Tyrosine. ### Explanation Amino acids are categorized into **essential** (must be obtained from the diet) and **nonessential** (can be synthesized by the human body). **Why Tyrosine is Correct:** **Tyrosine** is a nonessential amino acid because it is synthesized in the body from the essential amino acid **Phenylalanine** via the enzyme *phenylalanine hydroxylase*. While it is nonessential under normal conditions, it becomes "conditionally essential" in patients with Phenylketonuria (PKU), where the conversion pathway is defective. **Analysis of Incorrect Options:** * **Valine (B):** An essential branched-chain amino acid (BCAA). It is critical for muscle metabolism and tissue repair. * **Methionine (C):** An essential sulfur-containing amino acid. It serves as a precursor for cysteine and is the initiating amino acid in eukaryotic protein synthesis (encoded by the start codon AUG). * **Tryptophan (D):** An essential aromatic amino acid. It is the precursor for serotonin, melatonin, and niacin (Vitamin B3). **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Essential Amino Acids:** "PVT TIM HALL" (Phenylalanine, Valine, Threonine, Tryptophan, Isoleucine, Methionine, Histidine, Arginine*, Leucine, Lysine). * **Semi-essential Amino Acids:** Arginine and Histidine are considered semi-essential because they are required in larger quantities during periods of rapid growth or illness. * **Purely Ketogenic Amino Acids:** Leucine and Lysine (the only two that cannot be converted to glucose). * **Both Glucogenic and Ketogenic:** Phenylalanine, Tyrosine, Tryptophan, and Isoleucine (Aromatic amino acids + Isoleucine).

Q: Which of the following metabolic anomalies is seen in hemorrhagic shock?

Metabolic Acidosis. **Explanation:** **Why Metabolic Acidosis is the Correct Answer:** Hemorrhagic shock leads to a significant reduction in circulating blood volume, resulting in **decreased tissue perfusion** and systemic hypoxia. When tissues do not receive adequate oxygen, cells shift from aerobic metabolism to **anaerobic glycolysis**. This metabolic shift results in the excessive production of **Lactic Acid**. The accumulation of lactate and hydrogen ions consumes bicarbonate buffers, leading to a **High Anion Gap Metabolic Acidosis (HAGMA)**. This is a classic example of Type A Lactic Acidosis. **Why the Other Options are Incorrect:** * **Respiratory Acidosis:** This occurs due to alveolar hypoventilation (e.g., COPD, opioid overdose). In shock, the body typically compensates by *increasing* the respiratory rate (tachypnea) to blow off $CO_2$, which would move the pH in the opposite direction. * **Respiratory Alkalosis:** While early shock can cause hyperventilation (leading to low $PaCO_2$), the primary *metabolic anomaly* defining the pathology of shock is the acid buildup from hypoperfusion. * **Metabolic Alkalosis:** This is usually caused by acid loss (vomiting) or bicarbonate gain (diuretic use), which is the physiological opposite of the state seen in acute hemorrhage. **High-Yield Clinical Pearls for NEET-PG:** * **Lactate Levels:** Serum lactate is the most reliable biomarker for monitoring the severity of shock and the adequacy of resuscitation. * **Base Deficit:** A rising base deficit in a trauma patient is a sensitive indicator of occult shock and ongoing tissue hypoxia. * **The Lethal Triad of Trauma:** Acidosis, Hypothermia, and Coagulopathy. These three conditions exacerbate each other, significantly increasing mortality in hemorrhagic shock.

Q: Metabolic alkalosis is seen in which of the following conditions, except?

Methanol poisoning. **Explanation:** The correct answer is **Methanol poisoning**, as it causes **High Anion Gap Metabolic Acidosis (HAGMA)**, not alkalosis. **1. Why Methanol Poisoning is the Correct Answer:** Methanol is metabolized by alcohol dehydrogenase into **formaldehyde** and subsequently by aldehyde dehydrogenase into **formic acid**. The accumulation of formic acid leads to a significant increase in hydrogen ions, resulting in metabolic acidosis. This is typically associated with an increased anion gap and an osmolar gap. **2. Analysis of Other Options (Causes of Metabolic Alkalosis):** * **Vomiting:** Gastric juice is rich in Hydrochloric acid (HCl). Loss of stomach acid leads to a relative increase in bicarbonate levels in the blood, causing "chloride-responsive" metabolic alkalosis. * **Cushing’s Disease:** Excess cortisol has mineralocorticoid effects, leading to increased sodium reabsorption and increased secretion of Potassium ($K^+$) and Hydrogen ($H^+$) ions in the distal renal tubules. The loss of $H^+$ ions results in metabolic alkalosis. * **Diuretic Therapy:** Loop and thiazide diuretics cause the excretion of $Na^+$, $Cl^-$, and water. This leads to "contraction alkalosis" and increased distal delivery of sodium, which promotes $H^+$ secretion. **Clinical Pearls for NEET-PG:** * **Mnemonic for HAGMA:** **MUDPILES** (Methanol, Uremia, DKA, Paraldehyde, Iron/INH, Lactic acidosis, Ethylene glycol, Salicylates). * **Conn’s Syndrome & Cushing’s:** Both are classic endocrine causes of metabolic alkalosis associated with hypokalemia. * **Vomiting:** Characterized by **Hypochloremic, Hypokalemic Metabolic Alkalosis** with paradoxical aciduria.

Question 1

Which of the following biochemical changes is seen in primary hyperparathyroidism?

Accepted Answer

Increased Calcium, Decreased Phosphate

Answer

Decreased Calcium, Increased Phosphate

Answer

Increased Calcium, Increased Phosphate

Answer

Decreased Calcium, Decreased Phosphate

Question 2

Metabolic alkalosis is seen in all of the following conditions except:

Accepted Answer

Uretero-sigmoidostomy

Answer

Thiazide diuretic therapy

Answer

Prolonged vomiting

Answer

Cushing's disease

Question 3

A 50-year-old patient has the following blood gas values: pH = 7.05, HCO3 = 5 mEq/L, PCO2 = 12 mmHg, and BE = +30 mEq/L. How much sodium bicarbonate should be administered in the first hour?

Accepted Answer

100 mEq

Answer

150 mEq

Answer

250 mEq

Answer

500 mEq

Question 4

What is the normal route of calcium excretion?

Accepted Answer

Kidney and Intestine

Answer

Kidney

Answer

Kidney and Liver

Answer

Kidney, Intestine, and Pancreas

Question 5

Low calcium and high phosphate is seen in which condition?

Accepted Answer

Hypoparathyroidism

Answer

Hyperparathyroidism

Answer

Hyperthyroidism

Answer

Hypothyroidism

Question 6

Which of the following conditions is typically associated with a normal anion gap?

Accepted Answer

Renal tubular acidosis

Answer

Diabetic ketoacidosis

Answer

Lactic acidosis

Answer

Starvation ketoacidosis

Question 7

Which of the following is a nonessential amino acid?

Accepted Answer

Tyrosine

Answer

Valine

Answer

Methionine

Answer

Tryptophan

Question 8

Which of the following metabolic anomalies is seen in hemorrhagic shock?

Accepted Answer

Metabolic Acidosis

Answer

Respiratory Acidosis

Answer

Respiratory Alkalosis

Answer

Metabolic Alkalosis

Question 9

Lysis of cells causes which of the following electrolyte abnormalities?

Accepted Answer

Hypercalcemia

Answer

Hyperuricemia

Answer

Hyperphosphatemia

Answer

Hyperkalemia

Question 10

Metabolic alkalosis is seen in which of the following conditions, except?

Accepted Answer

Methanol poisoning

Answer

Cushing's disease

Answer

Vomiting

Answer

Diuretic therapy

Acid-Base and Electrolyte Balance — MCQs

Acid-Base and Electrolyte Balance — MCQs

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